Play with our interactive graphic to work out how many intelligent civilizations there could be in our universe.<p>Are we alone? It is a question that has occupied mankind for centuries.<p>Today, we live in an age of exploration, where robots on Mars and planet-hunting telescopes are beginning to allow …

Universe<p>Explore black holes, dark matter, stars, and many other astronomy topics.<p>Autumn night sky<p>Find out what you can see in the autumn night sky.<p>Gravitational lenses<p>Patrick Moore finds out how galaxies bend light.<p>The Sky at Night<p>Find out more about everyone's favourite astronomy programme.<p>Solar …